The present invention relates to a self-sacrifice type metal corrosion inhibitor for the corrosion proof treatment of the surface of the metal such as iron or iron alloy and a metal corrosion inhibiting method using said self-sacrifice type metal corrosion inhibitor.
Hitherto, a metal corrosion inhibitor comprising a metal powder having a greater ionization tendency than that of a metal to be treated such as zinc powder or aluminum powder in a case where said metal to be treated is iron or iron alloy, chromium (VI) source such as chromate and the like, pH adjusting agent such as metal oxide, metal hydroxide and the like, reducing organic compound such as low molecular oxohydroxy ether and the like, and water soluble solvent has been provided.
Said traditional metal corrosion inhibitor is adhered to the surface of a metal to be treated and chromium (VI) from said chromium (VI) source may be reduced by said reducing organic compound to chromium (III) to sedimentate on the surface of said metal to be treated by heating and said metal powder is adhered to, and fixed on the surface of said metal to be treated through said chromium (III) layer as an adhesive layer to form a metal corrosion inhibiting layer.
Hitherto, zinc-electro plating, zinc-mechanical plating and zinc-mechanical galvanized, zinc-melting plating and the like have been also used for the metal corrosion inhibiting treatment.
Said traditional metal corrosion inhibitor contains chromium (VI) source and in said zinc-electro plating, zinc-mechanical plating and zinc-mechanical galvanized, zinc-melting plating and the like also chromium (VI) is used to improve the metal corrosion inhibiting property. Nevertheless, said chromium (VI) is poisonous and it becomes difficult to use said chromium (VI) considering environmental contamination. Further said zinc-mechanical plating and zinc-mechanical galvanized has a problem of noise so that the advert of a self-sacrifice type metal corrosion inhibitor has been desired. Said self-sacrifice type metal corrosion inhibitor may contain no poisonous component and cause no public nuisance and no noise while said self-sacrifice type metal corrosion inhibitor has a metal corrosion inhibiting property equal to the traditional metal corrosion inhibitor containing chromium (VI) source.
Accordingly, an object of the present invention is to provide a self-sacrifice type metal corrosion inhibitor causing no public nuisance and no noise.
Another object of the present invention is to provide a self-sacrifice type metal corrosion inhibitor having a metal corrosion inhibiting property equal to the traditional metal corrosion inhibitor containing chromium (VI).
Briefly, said objects of the present invention can be attained by a self-sacrifice type metal corrosion inhibitor comprising;
one or more kind(s) of metal powder having a greater ionization tendency than that of a metal to be treated, water insoluble thermoplastic resin powder, water soluble anticorrosion agent, surface active agent, thickener and water; and
a metal corrosion inhibiting method comprising; preparing a treatment solution by dispersing said metal powder having a greater ionization tendency than that of said metal to be treated and said water insoluble thermoplastic resin powder in water containing said water soluble anticorrosion agent, said surface active agent and said thickener, adhering said treatment solution to the surface of said metal to be treated, heating said metal to be treated to melt said thermoplastic resin powder and form a thermoplastic resin layer fixed on the surface of said metal to be treated, and forming a metal corrosion inhibiting layer on the surface of said metal to be treated by fixing said metal powder on the surface of said metal to be treated through said thermoplastic resin layer as an adhesive layer; and further
a metal corrosion inhibiting method comprising; a treatment solution by dispersing said metal powder having a greater ionization tendency than that of said metal to be treated and said water insoluble thermoplastic resin powder in water containing said water soluble anticorrosion agent, said surface active agent and said thickener, adhering said treatment solution to the surface of said metal to be treated, heating said metal to be treated to melt said thermoplastic resin powder and form a thermoplastic resin layer fixed on the surface of said metal to be treated, and forming a metal corrosion inhibiting layer on the surface of said metal to be treated by fixing said metal powder on the surface of said metal to be treated through said thermoplastic resin layer as an adhesive layer; and further treating with a mixture of polymer and/or oligomer and Na2O:nSiO2 (n=3 or 4) as a self-restoring agent for the self-sacrifice type corrosion inhibiting property of said metal corrosion inhibiting layer wherein said polymer and/or oligomer is(are) one or more polymer or oligomer selected from a group consisting of poly (meth)acrylic acid, copolymer of (meth)acrylic acid and other vinyl monomer which can be copolymerized with (meth)acrylic acid, (meth)acrylic acid oligomer, and oligomer consisting of (meth)acrylic acid and other vinyl monomer which can be copolymerized with (meth)acrylic acid.
In a case where said metal to be treated is iron or iron alloy, zinc powder or aluminum powder or zinc-aluminum alloy powder is preferably used.
In said metal corrosion inhibitor of the present invention, said metal powder and said water insoluble thermoplastic resin powder are stably dispersed in water containing said water soluble anticorrosion agent, said surface active agent and said thickener.
When said treating solution is adhered on the surface of said metal to be treated and heated, said water insoluble thermoplastic resin is melted to adhere the surface of said metal to be treated and a metal corrosion inhibiting layer is formed. In said metal corrosion inhibiting layer, said thermoplastic resin powder maintains powder form since said thermoplastic resin powder is insoluble in water, the resulting thermoplastic resin layer on the surface of said metal to be treated has a porous structure. Accordingly said metal corrosion inhibiting layer consisting of said metal layer which is fixed on the surface of said metal to be treated by said thermoplastic resin layer also has a porous structure, and as a result said metal corrosion inhibiting layer becomes an electroconductive layer having a low electric resistance and a desirable electric resistance on the surface of said metal to be treated is guaranteed.
Further when said treated metal is further treated with a mixture of polymer and/or oligomer and Na2O:nSiO2 (n=3 or 4) as a self-restoring agent for the self-sacrifice type corrosion inhibiting property of said metal corrosion inhibiting layer wherein said polymer and/or oligomer is(are) one or more polymer or oligomer selected from a group consisting of poly (meth)acrylic acid, copolymer of (meth)acrylic acid and other vinyl monomer which can be copolymerized with (meth)acrylic acid, (meth)acrylic acid oligomer, and oligomer consisting of (meth)acrylic acid and other vinyl monomer which can be copolymerized with (meth)acrylic acid, to form an organo silicate compound layer on said metal corrosion inhibiting layer, a self-restoring property equal to or higher than that of zinc-chromate treatment layer is given to said metal corrosion inhibiting layer.
Said treatment solution consisting of only nonpoisonous components contains no poisonous component such as chromium (VI) source and the like.
Metal powder used in the present invention consists of a metal having a greater ionization tendency than that of a metal to be treated and in a case where said metal to be treated is iron or iron alloy, said metal powder may be zinc powder, aluminum powder, zinc-aluminum alloy powder and the like. The purity of said metal powder is preferably higher than 99.0% by weight, more preferably higher than 99.5% by weight and said metal powder has preferably powder form or flake form. In the case of zinc powder having flake form, the thickness is preferably less than 3 xcexcm, more preferably less than 2 xcexcm and the diameter is preferably less than 10 xcexcm, more preferably less than 7 xcexcm, and in the case of aluminum powder having flake form, the thickness is preferably less than 1 xcexcm, more preferably less than 0.5 xcexcm and the diameter is preferably less than 10 xcexcm, more preferably less than 7 xcexcm. The thinner is the better in each case where said metal powder has flake form.
Silver powder or silver flake, gold powder or gold flake, nickel powder or nickel flake, titanium powder or titanium flake, copper powder or copper flake and the like may be used instead of said metal powder or alloy powder or partially added to said metal powder or alloy powder.
Desirably, the surface of said metal powder may be treated with a treatment agent such as higher fatty acid, higher alcohol, wax having a high melting point, paraffine having a high melting point, antioxidant and the like. To treat the surface of said metal powder with said treatment agent, said metal powder may be dipped in a solution of said treatment agent using kerosine, mineral spirit, mineral terpin and the like as a solvent or said solution may be sprayed to said metal powder.
It is preferable to use zinc powder and aluminum powder together comparing the case where zinc powder or aluminum powder is singly used since when the surface of said metal to be treated is treated with zinc powder and aluminum powder together, zinc powder having a smaller ionization tendency and a higher specific gravity than aluminum may be migrated to the lower side of the treatment layer and aluminum may be migrated to the upper side of the treatment layer and as a result, a desirable self-sacrifice type metal corrosion inhibiting property is given to said surface of said treated metal.
Said metal powder may give a low electric resistance to said treatment layer and guarantee the preferable electroconductivity of the surface of said treated metal and said metal powder may be added in said treatment solution commonly in an amount between 1 to 75% by weight, desirably 5 to 40% by weight. In a case where the self-sacrifice type metal corrosion inhibiting property is very important, both zinc powder and aluminum powder are desirably used. In this case, the adding amount of zinc powder is desirably settled to be more than two times as the adding amount of aluminum, and the adding amount of zinc powder may be settled to be 1 to 30% by weight, desirably 5 to 25% by weight, and the adding amount of aluminum powder may be settled to be 1 to 25% by weight, desirably 2 to 15% by weight.
When silver, gold, nickel, titanium or copper is used as a material of said metal powder, the electric resistance of the resulting treatment layer may be much lower and the electroconductivity of said treatment layer may be much higher so that said treatment solution can be used in the electromagnetic wave shield treatment, photocatalyst, and the like besides the metal corrosion inhibiting treatment.
Water insoluble thermoplastic resin is used to adhere said metal powder to the surface of said metal to be treated and to adhere said metal powder together in the present invention. When water-soluble thermoplastic resin is used as an adhesive agent, said thermoplastic resin dissolves in water so that the surface of said metal to be treated may be wholly covered with said thermoplastic resin layer and non-electroconductive film of said thermoplastic resin layer may be formed between said metal powders and the surface of said metal to be treated, which inhibits the electroconductivity of said treatment layer and the self sacrifice type metal corrosion inhibiting property may not be produced sufficiently.
In the present invention, water insoluble thermoplastic resin powder is used not to inhibit the electroconductive ity of said treatment layer. The smaller particle size of said thermoplastic resin powder may result in the smaller using amount of said thermoplastic resin powder and adhesion of said metal powder together and between said metal powder and the surface of said metal to be treated may become more partial, resulting in an excellent electroconductivity and said treatment layer having self-sacrifice type metal corrosion inhibiting property may become finer and stronger.
Said water insoluble thermoplastic resin powder may be such as thermoplastic epoxy resin, polyethylene, polyvinylchloride, nylon resin such as nylon 6, nylon 66, nylon12, nylon 612, nylon 12 copolymer and the like, fluoro carbon resin such as PTFE, PFA, FED, teflon derivative and the like, epoxy-polyester copolymer, polyolefin thermoplastic elastomer such as TPE and the like, polycarbonate resin, polyacetal resin, melamine resin and the like.
Said water insoluble thermoplastic resin has been traditionally used in the powder coating process. The diameter of said thermoplastic resin powder is preferably less than 40 xcexcm, more preferably less than 20 xcexcm. The smaller diameter of said thermoplastic resin powder is better for the present invention. The using amount of said water insoluble thermoplastic resin powder may be 1 to 35% by weight, desirably 1 to 10% by weight.
Said water soluble anticorrosion agent used in the present invention has been traditionally used in cooling water for the radiator, the engine, and the like of the automobile and said water soluble anticorrosion agent is used for anticorrosion treatment of steel, cast iron, copper, copper alloy, solder, zinc, aluminum and the like. Many kinds of water soluble anticorrosion agent passing the anticorrosion ability test (metal corrosion test) JAOS-7014 can be used in the present invention.
Typically said water soluble anticorrosion agent may comprise an amide of lower fatty acid such as diethanol amide of hippuric acid, diethyl amide of hippuric acid, diethanol amide of saccinic acid amide and the like, and nitrite such as dicyclohexylamine nitrite, cyclohexyl amine nitrite, diethanol amine nitrite and the like. The adding amount of said water soluble anticorrosion agent may be commonly 0.1 to 10% by weight, desirably 0.5 to 3% by weight.
In the metal corrosion inhibitor of the present invention, a surface active agent is used to disperse said metal powder and said water insoluble thermoplastic resin powder in water stably.
Said surface active agent may be alkylaryl ether type nonionic surface active agents such as polyoxyethyleneno nylphenyl ether, polyoxyethyleneoctylphenyl ether and the like, alkyl ether type nonionic surface active agents such as polyoxyethylenebutyl ether, polyoxyethyleneoctylether, polyoxyethylenelauryl ether, polyoxyethyleneoleyl ether, polyoxyethylenestearyl ether, alkyl acetate type nonionic surface active agents such as polyoxyethylenelaurate, polyoxyethyleneo leate, polyoxyethylenestearate and the like, and ethylene oxide-propylene oxide block copolymer type nonionic surface active agents such as polypropylene glycol-polyethylene glycol ether and the like.
It is preferable to select a surface active agent containing no aryl group considering environmental hormone contamination. Further, it is preferable to select a surface active agent having H.L.B (Hydrophile-Lipophile Balance) value 7 to 18 more desirably 11 to 14. The adding amount of said surface active agent may be commonly 0.05 to 8% by weight, desirably 0.1 to 5% by weight.
Thickener should be added in said metal corrosion inhibitor of the present invention to ensure enough thickness of the coating layer of said treatment solution on the surface of said metal to be treated. Said thickener, used for this invention, is a water-soluble thickener comprising methyl cellulose, carboxymethylcellulose, hydroxymethylcellulose, ethyl cellulose, carboxymethylcellulose, hydroxyethylcellulose, poly(vinyl alcohol), starch, nonionic starch, pectin, guar gum, tamarind gum, locast bean gum, galactomannan, carrageenan, agar and the like. Further said carboxymethylcellulose, hydroxymethylcellulose, and hydroxyethylcellulose are more preferable as a thickener. The adding amount of said thickener may be commonly 0.05 to 5% by weight, desirably 0.1 to 1% by weight.
Water used to prepare said treatment solution of said metal corrosion inhibitor in the present invention may be such as distilled water, deionized water, further boiled city water and the like.
Since said treatment solution in said self-sacrifice type metal corrosion inhibitor of the present invention is nearly neutral, it is desirable to add a sterilizer to inhibit propagation of many kinds of microorganism such as bacteria, fungus, yeast, duckweed, and the like in the case of a long time storage. Said sterilizer to be selected has preferable compatibility with other components used in said treatment solution.
Said sterilizer used in the present invention may be isothiazoline and its derivative, organonitrogen-sulfur compound, organonitorogen compound, organonitrogen halogen compound, chlorohexidine salt, mixture of organonitrogen compound and organo sulfur halogen compound, mixture of organonitrogen compound and organonitrogen sulfur compound and the like. Desirable sterilizer may be isothiazolin and its derivative and chlorohexydine salt. Adding amount of said sterilizer may be commonly 0.01 to 5% by weight, desirably 0.01 to 1% by weight.
It is preferable to add on aqueous organic solvent to improve dispersing stability together with said anticorrosion agent and said surface active agent in said treatment solution of said corrosion inhibitor of the present invention. Said aqueous organic solvent may be 1-propanol, 2-propanol, primary butanol, secondary butanol, tertiary butanol, ethyleneglycol, diethyleneglycol, propyleneglycol, dipropyleneglycol, glycerol, methylcellosolve, ethyllcellosolve, butylcellosolve, methylcarbitol, ethylcarbitol, butylcarbitol, butyleneglycol, 2-ethyl-1,3-hexanediol, neopentylglycol, 1,5-pentanediol, 2,3-dimethyl-2,2-butanediol, and ethyleneglycol-mono-t-butyl ether, diacetone alcohol and the like. Further, said glycerol, ethyleneglycol, diethyleneglycol, propyleneglycol, butyleneglycol, dipropyleneglycol, 2-ethyl-1,3-hexanediol, and 1,5-pentanediol are more desirable as an aqueous organic solvent. Adding amount of said aqueous organic solvent may be commonly 3 to 40% by weight, desirably 8 to 35% by weight.
Said treatment solution of said corrosion inhibitor may be prepared by mixing said metal powder, said surface active agent, said water insoluble thermoplastic resin powder, said thickener and water, and desirably said aqueous organic solvent, said anticorrosion agent, and said sterilizer and stirring enough to disperse said metal powder in said treatment solution and the viscosity of said treatment solution is commonly adjusted 40xc2x15 sec by Iwata Ford cup #4. To treat the surface of said metal to be treated, first the surface of said metal is polished by shot blast, sand blast and the like and then desirably washed by an organic solvent such as n-hexane, xylene, methylethyl ketone, acetone, and the like followed by drying.
After that, said treatment solution is coated on the surface of said metal by dipping, spraying, roll coater, curtain flow coater, rotating blush coater, electrostatic coating and the like. After coating, said metal is kept at room temperature if necessary with blowing against said metal to dry and heat at a temperature between 150 to 160xc2x0 C. for at least 10 minutes for predrying and then at a temperature between 230 to 240xc2x0 C. for at least 10 minutes for main drying.
A self-sacrifice type metal corrosion inhibiting layer is formed on the surface of said metal by said treatment.
If desirable, paint may be further coated on said corrosion inhibiting layer. Further, aqueous paint can be prepared by adding inorganic pigment instead of said metal powder when said treatment solution is prepared and said aqueous paint can be used for coating on said corrosion inhibiting layer instead of common paint.
On said corrosion inhibiting layer, self-restoring treatment by using a self-restoring agent having self-sacrifice type corrosion inhibiting property may be desirably effected. Mixture, which is used for said self-restoring agent, comprises Na2O:nSiO2 (n=3 or 4) and polymer and/or oligomer which is one or more polymer and/or oligomer selected from the group consisting of poly acrylic and/or methacrylic acid (hereinafter referred to as (meth)acrylic acid), copolymer of (meth)acrylic acid and other vinyl monomer which can be copolymerized with (meth)acrylic acid, (meth)acrylic acid oligomer, and oligomer consisting of (meth)acrylic acid and other vinyl monomer which can be copolymerized with (meth)acrylic acid
As said other vinyl monomer which can be copolymerized with (meth)acrylic acid, one or more vinyl monomer can be used, wherein said one or more vinyl monomer is(are) one or more vinyl monomer comprising methyl (meth) acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth)acrylate, and diethylaminoethyl (meth)acrylate and the like. One or more kinds of said self-restoring agents may be used together.
Said self-restoring agent may be added in an amount of 0.1 to 20% by weight, desirably 1 to 5% by weight as a resin component of said polymer, and/or said copolymer and/or said oligomer, and Na2O:nSiO2 may be added in an amount of 20 to 45% by weight, desirably 25 to 35% by weight as SiO2.
By said self-restoring treatment, self-restoring property equal to or higher than that of zinc-chromate treatment layer can be given on said metal corrosion inhibiting layer.